Near-UV light can harm ocular tissues in a variety of ways. Several alterations in ocular tissue metabolism and chemistry were observed during this past year. Over a long period, as 1 1/2 years, mice exposed to subsolar levels of black light developed cataracts and degenerate retinas. Formation of proteins seemed to be inhibited in both tissues. In vitro, macromolecular synthesis (protein, RNA, DNA) by lenses, sea urchin egcs, and cultured mouse embryo cells was inhibited by near UV trypotophan photoproducts. Ocular tissue effects were enhanced when near-UV light was present along with the photoproducts, but sea urchin eggs and embryo cells were damaged even without added near-UV light. The addition of epinephrine to the aqueous humor led to physical and chemical alterations in its proteins when it was exposed to near-UV light for only a few hours. Thus the abiotic nature of near-UV light and its photoproducts was further emphasized.